Method of forming thin film and method of modifying surface of thin film

ABSTRACT

A method including: a plasma contact step including supplying treatment gas including a reactant gas into a chamber, activating a reactant component included in the treatment gas by generating plasma from the reactant component by applying high-frequency power, and bringing the treatment gas including the reactant component activated into contact with the surface of the substrate, in which in the plasma contact step, a first plasma generation condition in which stable plasma is generated by applying high-frequency power of a first power level while supplying treatment gas of a first concentration is changed to a second plasma generation condition in which a desired thin film is obtained by performing at least one of increasing the high-frequency power to a second power level and gradually decreasing the treatment gas to a second concentration, and of gradually increasing the high-frequency power to the second power level, and abnormal electrical discharge is suppressed.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates generally to a method of forming a thinfilm by a plasma-enhanced atomic layer deposition (PEALD) process, and amethod of modifying a surface of a thin film by using gas that issubjected to plasma generation.

Related Art

In a manufacturing step of a semiconductor device, a treatment such as afilm forming treatment is performed with respect to a substrate such asa semiconductor wafer. Examples of a film forming method include aplasma-enhanced atomic layer deposition (PEALD) process, and infilm-formation according to the PEALD process, a cycle is repeated inwhich a raw material gas component is adsorbed onto a substrate of afilm-forming target in a chamber while the substrate is heated, and thechamber is purged, and then, a reactant gas or a carrier gas issupplied, the reactant gas or the carrier gas is subjected to plasmageneration, a reactant component that is activated reacts with the rawmaterial gas component that is adsorbed on the substrate, and thus,atomic layers are deposited one by one, and as necessary, a surfacemodification treatment is performed by using the gas subjected to theplasma generation, and therefore, a desired thin film is formed on thesubstrate.

As such a film forming method, for example, a method of depositing asilicon oxide film on a substrate, including one or a plurality ofdeposition cycles including a step of supplying a plurality of pulses ofsilicon raw material gas including N,N,N′,N′-tetraethyl diaminosilane toa reactor, and a step of supplying oxygen-containing gas onto thesubstrate in the reactor has been disclosed (refer to Patent Document1).

Patent Document 1: U.S. Published Patent Application Publication, No.2009/041952, Specification

SUMMARY OF THE INVENTION

In an atomic layer deposition (ALD) process, a power level ofhigh-frequency power (RF power) that is applied at the time ofgenerating plasma, a supply condition of a carrier gas or a reactant gasthat is supplied into a chamber as a treatment gas, and the like areimportant parameters that affect film quality of a thin film to beobtained. In particular, it is possible to increase the quality of thethin film to be obtained by increasing the power level of thehigh-frequency power and optimizing the supply conditions of thereactant gas. But in the case of applying such high-frequency power at ahigh power level, plasma variation due to abnormal electrical dischargeoccurs resulting in a decrease in the quality of the film, and thus, itis difficult to obtain a desired thin film. In addition, in a process ofmodifying the surface of the thin film by using gas subjected to plasmageneration, in a case where the abnormal electrical discharge occurs, itis difficult to obtain desired thin film. Therefore, it is desirable togenerate stable plasma.

One aspect of the present disclosure is a method of forming a thin filmon a surface of a substrate, the method including:

a plasma contact step including

supplying a treatment gas including a reactant gas into a chamber,

activating a reactant component included in the treatment gas bygenerating plasma from the reactant component by applying high-frequencypower, and

bringing the treatment gas including the reactant component thusactivated into contact with the surface of the substrate to form thethin film, in which in the plasma contact step, a first plasmageneration condition is changed to a second plasma generation conditionby adjusting at least one of concentration of the reactant componentincluded in the treatment gas and power level of the high-frequencypower, thereby suppressing abnormal electrical discharge.

According to the aspect of the present disclosure, it is possible toprovide a method of forming a thin film in which, for example, even in acase where the reactant component included in the treatment gas issubjected to the plasma generation by applying plasma having a highpower level, stable plasma can be generated by suppressing abnormalelectrical discharge, and thus, a desired thin film can be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a vertical sectional view illustrating a film forming deviceas a substrate treatment device that is used in a method of forming athin film;

FIG. 2 is a graph showing an example of a power level of high-frequencypower (RF forward power (Fwd)) to be applied, an oxygen (O₂)concentration, and a self-bias voltage (Vdc), in a first embodiment;

FIG. 3 is a graph showing the power level of the high-frequency power(the RF forward power (Fwd)) to be applied, and the concentration ofoxygen (O₂) that is a reactant component, in Examples 1 to 6 of thepresent invention, and is a graph at the time of changing a duration formaintaining the power level after a concentration of the reactantcomponent reaches a second concentration (an RAMP time (1 second, 5seconds, and 9 seconds)) and a first concentration (20% and 5%) of thereactant component;

FIG. 4 is a graph showing a variation in the power level of thehigh-frequency power (the RF forward power (Fwd)), the oxygen (O₂)concentration, and a flow rate of raw material gas, in each step ofExamples 1 to 6 of the present invention;

FIG. 5 is a graph showing an example of the power level of thehigh-frequency power (the RF forward power (Fwd)) to be applied, theoxygen (O₂) concentration, and the self-bias voltage (Vdc), in a secondembodiment;

FIG. 6 is a graph showing the power level of the high-frequency power(the RF forward power (Fwd)) to be applied, and the concentration ofoxygen (O₂) as the reactant component, in Examples 7 to 12 of thepresent invention, and is a graph at the time of changing the durationfor maintaining the power level after the concentration of the reactantcomponent reaches the second concentration (the RAMP time (1 second, 5seconds, and 9 seconds)) and a first power level (0 W and 150 W);

FIG. 7 is a graph showing a variation in the power level of thehigh-frequency power (the RF forward power (Fwd)), the concentration ofoxygen (O₂), and the flow rate of the raw material gas, in each step ofExamples 7 to 12 of the present invention;

FIG. 8 is a graph at the time of changing the power level of thehigh-frequency power (the RF forward power (Fwd)) to be applied, theconcentration of oxygen (O₂) that is the reactant component, the firstconcentration (5% and 10%) of the reactant component, and the firstpower level (50 W and 150 W), in Examples 13 to 16 of the presentinvention;

FIG. 9 is a graph showing a variation in the power level of thehigh-frequency power (the RF forward power (Fwd)), the oxygen (O₂)concentration, and the flow rate of the raw material gas, in each stepof Comparative Example 1;

FIG. 10 is a graph showing a variation in the power level of thehigh-frequency power (the RF forward power (Fwd)), the oxygen (O₂)concentration, and the flow rate of the raw material gas, in each stepof Example 17 of the present invention;

FIG. 11 is a graph showing a variation in the power level of thehigh-frequency power (the RF forward power (Fwd)), the oxygen (O₂)concentration, and the flow rate of the raw material gas, in each stepof Example 18 of the present invention; and

FIG. 12 is a graph showing the power level of the high-frequency power(the RF forward power (Fwd)) to be applied, the oxygen (O₂)concentration, and the self-bias voltage (Vdc), in an aspect of therelated art.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, specific embodiments of the present invention will bedescribed in detail with reference to the drawings. Note that, thepresent invention is not limited to the following embodiments, but canbe variously changed within a range not departing from the gist of thepresent invention.

<<Method of Forming Thin Film>>

A method of forming a thin film according to this embodiment is a methodof forming a thin film, including: a plasma contact step of supplyingtreatment gas including reactant gas into a chamber, of activating areactant component (a gas component that is activated by the plasmageneration) included in the treatment gas by generating plasma from thereactant component by applying high-frequency power, and of bringing thetreatment gas including the reactant component thus activated by theplasma generation into contact with the surface of the substrate to formthe thin film, in which in the plasma contact step, a first plasmageneration condition is changed to a second plasma generation conditionby adjusting one or both of a concentration of the reactant component inthe treatment gas and a power level of the high-frequency power, therebysuppressing abnormal electrical discharge.

In the method of forming a thin film according to this embodiment,first, stable plasma is generated in the first plasma generationcondition or a condition close thereto, and thus, even in a case wherethe first plasma generation condition is changed to the second plasmageneration condition by adjusting at least one of the concentration ofthe reactant component in the treatment gas and the power level of thehigh-frequency power, the generation of the stable plasma is maintained,and generation of plasma from the reactant component included in thetreatment gas is accelerated by adjusting the concentration of thereactant component or the power level of the high-frequency power. Forthis reason, it is possible to provide a method of forming a thin filmin which even in a case where the reactant component included in thetreatment gas is subjected to the plasma generation by applying plasmahaving a high power level, abnormal electrical discharge due toparasitic plasma or the like can be suppressed, and stable plasma can begenerated.

In the method of forming a thin film according to this embodiment, thethin film is prepared by a plasma-enhanced atomic layer deposition(PEALD) process including a supply step of supplying at least the rawmaterial gas including a raw material component into the chamber and ofadsorbing the raw material gas component on a surface of the substrate,a discharge step of discharging any of the raw material gas componentthat is not adsorbed on the substrate from the chamber. And the plasmacontact step described above, and a PEALD process progresses on thebasis of a surface reaction that is controlled, in general,self-controlled. Here, a reaction between the raw material gas and thereactant gas that are included in the treatment gas, in a gas phase, canbe reduced by alternately performing the supply of the raw material gaswith respect to the substrate and the contact of the reactant gas orcarrier gas that is subjected to the plasma generation by theapplication of the high-frequency power with respect to the substrate.According to the PEALD process of this embodiment, it is possible toform a thin film having a high step coverage, and thus, it is possibleto preferably form the thin film on a three-dimensional structure on thesubstrate.

Herein, a “thin film of high film quality” indicates a thin film havinghigh film quality, and more specifically, indicates a thin film having asmall wet etch rate ratio (WERR). Here, the WERR of the thin film is aratio of mass decrease in an ALD film to a mass decrease in the TOX filmat the time of simultaneously dipping the ALD film and a thermal oxidefilm thereof (the TOX film) in diluted hydrofluoric acid. And anumerical range at the time of forming a SiO₂ film as the ALD film ispreferably less than 2.0, is more preferably less than or equal to 1.9,and is even more preferably less than or equal to 1.6.

In addition, herein, “stable plasma” indicates plasma that does notcause abnormal electrical discharge. The presence or absence of theabnormal electrical discharge at the time of applying the high-frequencypower can be determined in accordance with a positive or negative valueof a self-bias voltage (Vdc). Here, in a case where the abnormalelectrical discharge occurs at the time of applying the high-frequencypower, the self-bias voltage (Vdc) has a positive value. In addition, ina case where the abnormal electrical discharge does not occur even atthe time of applying the high-frequency power, the self-bias voltage(Vdc) has 0 or a negative value.

<Film Forming Device>

A film forming device that is used in the method of forming a thin filmaccording to this embodiment and a surface modification treatment methodof a thin film is not particularly limited. But for example, a filmforming device 1 as illustrated in FIG. 1 can be used.

FIG. 1 is a vertical sectional view schematically illustrating a filmforming device as a substrate treatment device according to anembodiment of the present invention. In the film forming device 1 ofFIG. 1 , a thin film is formed on a substrate W such as a semiconductorwafer by a plasma-enhanced atomic layer deposition (PEALD) process.

The film forming device 1 includes an approximately cylindrical chamber10 with a bottom of which the upper side is opened, and an installationstand 12 provided in the chamber 10, on which the substrate W isinstalled.

The chamber 10 is electrically grounded by a grounding wire that is notillustrated. In addition, an inner wall of the chamber 10, for example,is covered with a coated film (not illustrated) formed of a plasmaresistant material on a surface.

The installation stand 12, for example, is formed of a metal materialsuch as nickel. A lower surface of the installation stand 12 issupported by a support member 13 formed of a conductive material, and iselectrically connected thereto. The support member 13 is electricallyconnected to a bottom surface of the chamber 10. For this reason, theinstallation stand 12 is grounded through the chamber 10, and functionsas a lower electrode pairing with a gas supply unit 14 that functions asan upper electrode. A heater (not illustrated) is embedded in theinstallation stand 12, and thus, it is possible to heat the substrate Wthat is installed on the installation stand 12 to a predeterminedtemperature.

Here, the size of an air gap D between the installation stand 12 thatfunctions as the lower electrode and the gas supply unit 14 thatfunctions as the upper electrode may be in a range in which plasma canbe generated between the installation stand 12 and the gas supply unit14, and for example, can be in a range of greater than or equal to 7 mmand less than or equal to 15 mm.

A lower portion of the support member 13 extends to the lower sidethrough an insertion hole 11 that is formed in the central portion of abottom portion of the chamber 10. The support member 13 can be moved upand down by a hoisting and lowering mechanism that is not illustrated,and thus, the installation stand 12 is hoisted or lowered.

In addition, a plurality of support pins (not illustrated) are providedon the lower side of the installation stand 12 and the inner side of thechamber 10. And insertion holes (not illustrated) into which the supportpins are inserted are formed on the installation stand 12. When theinstallation stand 12 is lowered, the substrate W can be received byupper end portions of the support pins that penetrate through theinsertion holes of the installation stand 12. And the substrate W can betransferred from or to a transport arm (not illustrated) that entersfrom the outside the chamber 10.

The gas supply unit 14 is provided on the upper side of the installationstand 12 in parallel to face the installation stand 12. In other words,the gas supply unit 14 is disposed to face the substrate W that isinstalled on the installation stand 12. The gas supply unit 14 suppliestreatment gas for performing a treatment with respect to the substrateW, and for example, is formed of a conductive metal such as nickel (Ni),and also functions as the upper electrode.

An outer circumferential portion of an upper surface of the gas supplyunit 14 is retained by an annular support member 16. The support member16, for example, is formed of an insulating material such as quartz. Thegas supply unit 14 and the chamber 10 are electrically insulated. Notethat, a heater (not illustrated) may be provided on the upper surface ofthe gas supply unit 14.

A supply source (not illustrated) of the raw material gas or thereactant gas and the carrier gas that are the treatment gas is connectedto the gas supply unit 14 through an external gas supply pipe of thefilm forming device 1. The raw material gas or the reactant gas, and thecarrier gas that are supplied to the gas supply unit 14 are introducedto the chamber 10 through the gas supply hole 15 in the shape of ashower. Further, a gas supply condition adjustment unit including avalve, a mass flow controller, and the like is provided in the externalgas supply pipe of the film forming device 1, and is capable ofadjusting a gas supply condition of the treatment gas, such as a gastype, a gas mixing ratio, and a flow rate.

In addition, the gas supply unit 14 functions as the upper electrode. Ahigh-frequency power source that supplies high-frequency power andgenerates plasma is electrically connected to the gas supply unit 14through a matching box (not illustrated). The high-frequency powersource, for example, is configured such that high-frequency power havinga frequency of 100 kHz to 100 MHz can be output. The matching boxmatches internal impedance to load impedance of the high-frequency powersource, and when plasma is generated in the chamber 10, it seems thatthe internal impedance and the load impedance of the high-frequencypower source are identical to each other.

In addition, an exhaust mechanism that exhausts the inside of thechamber 10 is connected to a side surface of the chamber 10. Theenvironment in the chamber 10 can be exhausted by driving the exhaustmechanism, and the pressure can be reduced to a predetermined vacuumdegree.

First Embodiment of Method of Forming Thin Film

In a first embodiment of the method of forming a thin film according tothis embodiment, a thin film is prepared on the substrate by theplasma-enhanced atomic layer deposition (PEALD) process. And when thereactant component (the gas component that is activated by the plasmageneration) of the treatment gas is subjected to the plasma generationby applying the high-frequency power into the chamber, the first plasmageneration condition in which high-frequency power of a second powerlevel that is identical to that of the second plasma generationcondition described below is applied while the treatment gas in whichthe concentration of the reactant component is the first concentrationis supplied is changed to the second plasma generation condition bygradually decreasing the concentration of the reactant component to asecond concentration from the first concentration while applying thehigh-frequency power of the second power level.

[Substrate and Preparation Thereof]

In forming a thin film, first, the substrate W is taken into the chamber10, and is installed and retained on the installation stand 12. Asilicon substrate, a germanium substrate, and the like can be used asthe substrate W. But the substrate W is not limited thereto. Inaddition, the substrate W is taken into the chamber 10 in a vacuum stateby using a load lock chamber or the like that is not illustrated.

The substrate W that is installed on the installation stand 12 is heatedby using a heater. Here, a heating temperature of the substrate W, forexample, can be in a range of 50° C. to 500° C. At this time, thecarrier gas is supplied into the chamber 10. Here, for example, at leastone selected from the group consisting of helium (He) gas, argon (Ar)gas, and hydrogen (H₂) gas can be used as the carrier gas. At this time,an internal pressure of the chamber 10, for example, can be in a rangeof greater than or equal to 50 Pa, and can be preferably in a range ofgreater than or equal to 300 Pa. And an upper limit thereof can be in arange of less than or equal to 1300 Pa, and can be preferably in a rangeof less than or equal to 1000 Pa. Note that, the reactant gas describedbelow may be supplied along with the carrier gas.

[Raw Material Gas Supply Step]

Next, at least the raw material gas is supplied into the chamber 10. Atthis time, the carrier gas or the reactant gas may be supplied to thechamber 10 along with the raw material gas. Accordingly, the rawmaterial gas is adsorbed onto the substrate W, and thus, a molecularlayer of the raw material gas is formed on the surface of the substrateW. Here, examples of the raw material gas including materials that canbe used in the plasma-enhanced atomic layer deposition (PEALD) process,it is preferable to use aminosilane, and more specifically, it ispossible to use at least one selected from the group consisting ofbis(diethyl amino)silane (BDEAS), diisopropyl aminosilane (DIPAS),tetrakis(dimethyl amino)silane (4DMAS), tris(dimethyl amino)silane(3DMAS), bis(dimethyl amino)silane (2DMAS), tetrakis(ethyl methylamino)silane (4EMAS), tris(ethyl methyl amino)silane (3EMAS),bis(tart-butyl amino)silane (BTBAS), and bis(ethyl methyl amino)silane(BEMAS). In addition, a flow rate of the raw material gas to be suppliedinto the chamber 10 can be approximately in a range of greater than orequal to 25 sccm. And can be preferably in a range of greater than orequal to 50 sccm, and an upper limit thereof can be approximately in arange of less than or equal to 3000 sccm, and can be preferably in arange of less than or equal to 2000 sccm. In addition, a supply time ofthe raw material gas, for example, can be in a range of longer than orequal to 0.05 seconds, and can be preferably in a range of longer thanor equal to 0.2 seconds. And an upper limit thereof can be in a range ofshorter than or equal to 5.0 seconds, and can be preferably in a rangeof shorter than or equal to 0.5 seconds. An optimal supply time of theraw material gas can be set on the basis of a condition such as the typeof raw material gas and the internal pressure of the chamber.

[Purge Step]

An excessive raw material gas component that is not adsorbed on thesubstrate W is discharged from the chamber after the raw material gas issupplied (a purge step or discharge step). Accordingly, thecontamination of the thin film due to the raw material gas remaining inthe environment is reduced, and thus, it is possible to obtain a flatterthin film. Here, examples of a section of discharging the raw materialgas component that is not adsorbed on the substrate W from the chamberinclude a section of purging the raw material gas component that is notadsorbed on the substrate W by supplying the reactant gas, the carriergas, or mixed gas of the reactant gas and the carrier gas into thechamber 10, a section of discharging the raw material gas component byvacuuming the chamber 10, and a combination thereof. Among them, inparticular, it is preferable that the raw material gas component ispurged by supplying gas including the reactant gas into the chamber 10,and it is more preferable that the raw material gas component is purgedby supplying the treatment gas described below. As described above, theraw material gas component that is not adsorbed on the substrate W isdischarged from the chamber 10, and thus, the contamination of the thinfilm due to the raw material gas remaining in the environment of thechamber 10 is reduced, and therefore, it is possible to obtain a flatterthin film. In particular, the raw material gas component is purged at aratio at the time of starting the application of the high-frequencypower, and thus, it is possible to smoothly perform the generation ofplasma described below and the formation of a thin film.

[Plasma Contact Step]

Next, the treatment gas including the reactant gas is supplied into thechamber 10, and the high-frequency power is applied to the gas supplyunit 14, and thus, the reactant component (the gas component that isactivated by the plasma generation) of the treatment gas is subjected tothe plasma generation. Then, the reactant component that is activated bythe plasma generation, included in the treatment gas reacts with the rawmaterial gas component that is adsorbed on the substrate W by bringingthe treatment gas including the reactant component that is activated bythe plasma generation into contact with the surface of the substrate W,and thus, even in a case where the surface of the substrate W has athree-dimensional structure, it is possible to form a thin film having auniform thickness on the surface.

For example, in a case where the reactant gas and the carrier gas aresupplied into the chamber 10, as the treatment gas, the reactantcomponent consisting of at least one of the reactant gas and the carriergas is subjected to the plasma generation by applying the high-frequencypower, and the reactant component reacts with the raw material gascomponent by bringing the reactant component that is activated by theplasma generation into contact with the raw material gas component thatis adsorbed on the substrate W, and thus, it is possible to form a thinfilm having a uniform thickness on the surface of the substrate W.

In this embodiment, when plasma is generated by applying thehigh-frequency power, stable plasma is generated in the first plasmageneration condition in which the high-frequency power of the secondpower level that is identical to that of the second plasma generationcondition is applied while the treatment gas in which the concentrationof the reactant component is the first concentration is supplied, andthen, the first plasma generation condition is changed to the secondplasma generation condition in which a thin film of high film quality isformed by gradually decreasing the concentration of the reactantcomponent included in the treatment gas that is supplied to the chamber10 to the second concentration from the first concentration whileapplying the high-frequency power of the second power level.

In the second plasma generation condition in which a thin film of highfilm quality is formed, even in the case of generating plasma byapplying the high-frequency power to the treatment gas in which theconcentration of the reactant component is low, as it is obvious fromthe fact that the self-bias voltage (Vdc) has a positive value, theabnormal electrical discharge easily occurs, and there are many caseswhere it is difficult to generate stable plasma (FIG. 12 ). From such aviewpoint, in the method of forming a thin film of this embodiment, inthe first plasma generation condition, stable plasma is generated byapplying the high-frequency power (RF forward power (Fwd)) to thetreatment gas in which the concentration of the reactant component isrelatively high, and then, the first plasma generation condition ischanged to the second plasma generation condition in which a thin filmof high film quality is formed by gradually decreasing the concentrationof the reactant component (for example, a concentration of oxygen (O₂)gas) to the second concentration, and thus, in the second plasmageneration condition, the generation of stable plasma is alsomaintained. For this reason, the self-bias voltage (Vdc) has a negativevalue, and thus, it is possible to generate stable plasma without anyabnormal electrical discharge (FIG. 2 ).

Gas that is capable of reacting with the raw material gas describedabove in the presence of the gas component that is subjected to theplasma generation can be used as the reactant gas included in thetreatment gas. More specifically, it is preferable to use at least oneselected from the group consisting of oxygen (O₂) gas, nitrous oxide(N₂O) gas, carbon dioxide (CO₂) gas, nitrogen (N₂) gas, and ammonia(NH₃) gas. In addition, as described above, it is preferable to use atleast one selected from the group consisting of helium (He) gas, argon(Ar) gas, and hydrogen (H₂) gas, as the carrier gas.

The first concentration of the reactant component included in thetreatment gas, for example, can be in a range of greater than or equalto 3 volume %, and can be preferably in a range of greater than or equalto 5 volume %. And an upper limit thereof can be in a range of less thanor equal to 50 volume %, and can be preferably in a range of less thanor equal to 20 volume %. In addition, the second power level of thehigh-frequency power (the RF forward power (Fwd)), for example, can bein a range of greater than or equal to 100 W, and can be preferably in arange of greater than or equal to 200 W. And an upper limit thereof canbe in a range of less than or equal to 1000 W, and can be preferably ina range of less than or equal to 500 W. In particular, the firstconcentration is set to be greater than or equal to 20 volume %, andthus, even in the case of applying high-frequency power of greater thanor equal to 100 W at which a thin film of high film quality can beformed, it is difficult to cause the abnormal electrical discharge, andtherefore, it is possible to generate stable plasma in a state ofapplying the high-frequency power. On the other hand, the firstconcentration is set to be less than or equal to 20 volume %, and thus,when the concentration of the reactant component is decreased to thesecond concentration, it is possible to reduce fluctuations in theconcentration of the reactant component, and therefore, it is possibleto increase the productivity of the film forming device 1.

In addition, the second concentration of the reactant component includedin the treatment gas is a value that is lower than the firstconcentration, and for example, can be in a range of greater than orequal to 1 volume %. And can be preferably in a range of greater than orequal to 2 volume %, and an upper limit thereof can be in a range ofless than or equal to 10 volume %, and can be preferably in a range ofless than or equal to 5 volume %. The concentration range is a range inwhich a thin film of high film quality can be formed, but is also aconcentration range in which it is difficult to generate stable plasma,in particular, at the time of applying the high-frequency power of thesecond power level. In the method according to this embodiment, even ina case where the concentration of the reactant component included in thetreatment gas to be supplied to the chamber 10 is decreased to thesecond concentration from the first concentration, stable plasma iscontinuously generated, and thus, it is difficult to cause the abnormalelectrical discharge, and it is possible to form a thin film of highfilm quality.

In addition, when the concentration of the reactant component includedin the treatment gas is decreased to the second concentration from thefirst concentration, a rate of change of the concentration of thereactant component as a function of time, for example, can be in a rangeof greater than or equal to 0.3 volume %/second, and can be preferablyin a range of greater than or equal to 0.5 volume %/second. And an upperlimit thereof can be in a range of less than or equal to 100 volume%/second, and can be preferably in a range of less than or equal to 80volume %/second. In particular, the rate of change of the concentrationis set to be greater than or equal to 1 volume %/second, and thus, it ispossible to make the occurrence of the abnormal electrical discharge dueto the application of the high-frequency power difficult.

A duration to apply the high-frequency power after the concentration ofthe reactant component reaches the second concentration, for example,can be in a range of longer than or equal to 0.05 seconds, and can bepreferably in a range of longer than or equal to 0.2 seconds. And anupper limit thereof can be in a range or shorter than or equal to 600seconds, and can be preferably in a range or shorter than or equal to 20seconds.

Examples of a section of adjusting the concentration of the reactantcomponent include changing a supply ratio of the reactant component thatis subjected to the plasma generation, and a non-reactant component thatis not subjected to the plasma generation. For example, in a case wherethe reactant component consists of the reactant gas, changing a supplyratio of the reactant gas and the carrier gas with respect to thechamber 10 is exemplified. At this time, a supply amount of the reactantgas with respect to the chamber 10 may be decreased, or a supply amountof the carrier gas may be increased.

A flow rate of the treatment gas that is supplied to the chamber 10 atthe time of forming a thin film is not particularly limited, but can beapproximately in a range of greater than or equal to 1500 sccm, and canbe preferably in a range of greater than or equal to 2500 sccm. And anupper limit thereof can be in a range of less than or equal to 7500sccm, and can be preferably in a range of less than or equal to 5000sccm.

The internal pressure of the chamber 10 at the time of forming a thinfilm may be a size in a range that can be applied to the plasma-enhancedatomic layer deposition (PEALD) process, but is not particularlylimited, and for example, can be in a range of greater than or equal to100 Pa, and can be preferably in a range of greater than or equal to 200Pa. And an upper limit thereof can be in a range of less than or equalto 1000 Pa, and can be preferably in a range of less than or equal to800 Pa.

The reactant component included in the treatment gas is activated by theplasma generation of the reactant component included in the treatmentgas, and for example, radicals of the reactant gas or the carrier gas,atoms of the reactant gas or the carrier gas, and plasma of the reactantgas or the carrier gas are generated. Then, the reactant gas that isactivated by plasma generation, included in the treatment gas reactswith the raw material gas component that is adsorbed on the substrate,and thus, it is possible to form a single layer of a thin film.

[By-Product Discharge Step]

The single layer of the thin film is formed, and then, a by-product thatis generated by a reaction between the reactant component and the rawmaterial gas component is discharged from the chamber. Here, examples ofa section of discharging the by-product from the chamber include asection of supplying at least one of the reactant gas and the carriergas into the chamber 10 and of purging the raw material gas componentthat is not adsorbed on the substrate, a section of vacuuming thechamber 10 and of discharging the raw material gas component, and acombination thereof.

[Formation of Thin Film Having Desired Thickness]

The by-product is discharged from the chamber 10, and then, a cycle isrepeated in which the raw material gas component is adsorbed on thesubstrate W, the excessive raw material gas component is discharged fromthe chamber 10, the treatment gas including the reactant gas is suppliedinto the chamber 10, the reactant component in the treatment gas issubjected to the plasma generation by applying the high-frequency powerto the gas supply unit 14 and reacts with the raw material gas componentto form a thin film. And the by-product is discharged from the chamber,and thus, it is possible to form a thin film having a desired thicknesson the substrate W. Here, the thickness of the thin film is thethickness of a monomolecular layer, and can be in a range of greaterthan or equal to 0.0001 μm. And an upper limit thereof can be in a rangeof less than or equal to 1 μm, and can be preferably in a range of lessthan or equal to 0.1 μm.

Examples of the thin film that is obtained by this embodiment include aSiO₂ film, a SiN film, or a SiC film. Such a thin film that is useful ina semiconductor device is formed by the plasma-enhanced atomic layerdeposition (PEALD) process, and thus, it is possible to obtain asemiconductor device with higher quality and high reliability.

Second Embodiment of Method of Forming Thin Film

In a second embodiment of the method of forming a thin film according tothis embodiment, the thin film is prepared on the substrate by theplasma-enhanced atomic layer deposition (PEALD) process. And in theplasma contact step, when the reactant component in the treatment gas issubjected to the plasma generation by applying the high-frequency powerinto the chamber, the first plasma generation condition in which thehigh-frequency power of the first power level is applied or thehigh-frequency power is not applied while the treatment gas in which theconcentration of the reactant component is the second concentration thatis identical to that of the second plasma generation condition describedbelow is supplied is changed to the second plasma generation conditionby gradually increasing the power level of the high-frequency power tothe second power level while supplying the treatment gas of the secondconcentration.

In the method of forming a thin film of this embodiment, theconcentration of the reactant component included in the treatment gas(for example, oxygen (O₂) gas) in the first plasma generation conditionis the second concentration at which a thin film of high film qualitycan be formed, and the first power level of the high-frequency power islower than a power level at which a thin film of high film quality canbe formed. Stable plasma is generated at a power level that is close tothe first plasma generation condition and is relatively low by graduallyincreasing the power level of the high-frequency power (the RF forwardpower (Fwd)) from such a first plasma generation condition, and then,the power level is gradually increased to the first power level at whicha thin film of high film quality can be formed, and thus, the generationof stable plasma is maintained. For this reason, the self-bias voltage(Vdc) has a negative value, and it is possible to generate stable plasmawithout any abnormal electrical discharge (FIG. 5 ).

Here, the first power level that is applied before the high-frequencypower is gradually increased is not particularly limited, and forexample, may be gradually increased from 0 W (a state in which thehigh-frequency power is not applied). On the other hand, from theviewpoint of reducing a time required for increasing the high-frequencypower while making the occurrence of the abnormal electrical dischargedifficult, the first power level, for example, can be in a range ofgreater than or equal to 50 W, and can be preferably in a range ofgreater than or equal to 100 W. An upper limit of the first power levelcan be in a range of less than or equal to 1000 W, and can be preferablein a range of less than or equal to 500 W. In particular, the firstpower level is set to be less than or equal to 1000 W, and thus, even ina case where the second concentration is high, it is difficult to causethe abnormal electrical discharge, and therefore, it is possible togenerate stable plasma.

In addition, the second concentration of the reactant component includedin the treatment gas, for example, can be in a range of greater than orequal to 1 volume %, and can be preferably in a range of greater than orequal to 2 volume %. And an upper limit thereof can be in a range ofless than or equal to 20 volume %, and can be preferably in a range ofless than or equal to 10 volume %.

On the other hand, the second power level after the high-frequency poweris increased is a value higher than the first power level, and forexample, can be in a range of greater than or equal to 100 W, and can bepreferably in a range of greater than or equal to 200 W. And an upperlimit thereof can be in a range of less than or equal to 1500 W, and canbe preferably in a range of less than or equal to 1000 W. The range ofthe power level is a range in which a thin film of high film quality canbe formed at a concentration range in which it is difficult to generatestable plasma, in particular, at the time of supplying the treatment gasin which the concentration of the reactant component is the secondconcentration into the chamber 10. In the method according to thisembodiment, the power level of the high-frequency power to be applied isgradually increased to the second power level from the first powerlevel, and thus, stable plasma is continuously generated, and therefore,it is difficult to cause the abnormal electrical discharge, and it ispossible to form a thin film of high film quality.

In addition, a rate of change of the high-frequency power at the time ofincreasing the high-frequency power to the second power level, forexample, can be in a range of greater than or equal to 5 W/second, andcan be preferably in a range of greater than or equal to 8 W/second. Andan upper limit thereof can be in a range of less than or equal to 5000W/second, and can be preferably in a range of less than or equal to 3000W/second. In particular, the rate of change of the high-frequency poweris set to be less than or equal to 10 W/second, and thus, it is possibleto make the occurrence of the abnormal electrical discharge due to theapplication of the high-frequency power difficult.

A duration to apply the high-frequency power after the power level ofthe high-frequency power reaches the second power level, for example,can be in a range of longer than or equal to 0.05 seconds, and can bepreferably in a range of longer than or equal to 0.2 seconds. And anupper limit thereof can be in a range of shorter than or equal to 600seconds, and can be preferably in a range of shorter than or equal to 20seconds.

The type of the reactant gas and the carrier gas included in thetreatment gas, a flow rate of the reactant gas and the carrier gas atthe time of forming a thin film, and the internal pressure of thechamber 10 are not particularly limited, and for example, can be in thesame range as that of the first embodiment.

Third Embodiment of Method of Forming Thin Film

The methods of forming a thin film according to the first embodiment andthe second embodiment may be combined with each other. In a thirdembodiment of the method of forming a thin film according to thisembodiment, suppressing the abnormal electrical discharge by graduallydecreasing the concentration of the reactant component in the firstembodiment to the second concentration and suppressing the abnormalelectrical discharge by gradually increasing the power level of thehigh-frequency power in the second embodiment to the second power levelare combined. More specifically, in the plasma contact step, when thereactant component in the treatment gas is subjected to the plasmageneration by applying the high-frequency power into the chamber, thefirst plasma generation condition in which the high-frequency power ofthe first power level is applied or the high-frequency power is notapplied while the treatment gas in which the concentration of thereactant component is the first concentration is supplied is changed tothe second plasma generation condition by gradually increasing the powerlevel of the high-frequency power to the second power level from thefirst power level, and by gradually decreasing the concentration of thereactant component to the second concentration from the firstconcentration.

In the method of forming a thin film of this embodiment, theconcentration of the reactant gas to be supplied is set to the secondconcentration at which a thin film of high film quality can be formedfrom the first concentration at which stable plasma is generated, andthe high-frequency power is gradually increased to the second powerlevel at which a thin film of high film quality can be formed from thefirst power level at which stable plasma is generated, and thus, stableplasma is generated in the condition of the reactant gas concentrationand the power level in which stable plasma is generated, and then, thecondition is adjusted to the condition of the reactant gas concentrationand the power level in which a thin film of high film quality can beformed, and therefore, the generation of stable plasma is maintained.For this reason, the self-bias voltage (Vdc) has a negative value, andit is possible to generate stable plasma without any abnormal electricaldischarge.

In the method of forming a thin film of this embodiment, both of theconcentration of the reactant component included in the treatment gas,and the power level of the high-frequency power are varied, and thus, itis possible to decrease a variation range thereof, compared to a casewhere the concentration of the reactant component is independentlyvaried or a case where the power level of the high-frequency power isindependently varied. For this reason, the first concentration and thesecond concentration of the concentration of the reactant componentincluded in the treatment gas can be values in the same numerical rangeas that of the first embodiment described above, and the first powerlevel. And the second power level of the high-frequency power (the RFforward power (Fwd)) can be values in the same numerical range as thatof the second embodiment described above.

<<Method of Modification of Surface of Thin Film>>

On the other hand, a method of modifying a surface of a thin filmaccording to this embodiment is a method of modifying a surface of athin film including the plasma contact step of supplying the treatmentgas including at least one of the reactant gas and the carrier gas intothe chamber, of activating the treatment gas by generating plasma byapplying the high-frequency power, of bringing the treatment gas that isactivated by the plasma generation into contact with the surface of thethin film that is formed on the substrate to modify the surface of thethin film, in which the plasma contact step is a surface modificationstep in which a third plasma generation condition is changed to a fourthplasma generation condition by adjusting at least one of concentrationof a reactant component in the treatment gas and power level of thehigh-frequency power, thereby modifying the surface of the thin filmwhile suppressing abnormal electrical discharge.

In the method of modifying a surface of a thin film according to thisembodiment, first, stable plasma is generated in the third plasmageneration condition or in a condition close thereto, and thus, even ina case where the third plasma generation condition is changed to thefourth plasma generation condition by adjusting at least one of theconcentration of the reactant component included in the treatment gasand the power level of the high-frequency power, the generation of thestable plasma is maintained, and generation of plasma from the reactantcomponent included in the treatment gas is accelerated by adjusting theconcentration of the reactant component or the power level of thehigh-frequency power. According to the method of this embodiment, it ispossible to perform the surface modification treatment with respect tothe thin film by using stable plasma of a higher concentration, andthus, it is possible to efficiently perform a desired surfacemodification treatment.

[Substrate and Preparation Thereof]

The substrate W on which a thin film is deposited is installed andretained on the installation stand 12 of the chamber 10. Here, a siliconsubstrate, a germanium substrate, and the like can be used as thesubstrate W, but the substrate W is not limited thereto. In addition,examples of the thin film that is deposited on the substrate W include aSiO₂ film, a SiN film, or a SiC film. In addition, a method ofdepositing the thin film on the substrate W is not particularly limited,but the plasma-enhanced atomic layer deposition (PEALD) process ispreferable since the thin film is deposited on a surface, and then, canbe directly subjected to the surface modification treatment.

The substrate W that is installed on the installation stand 12 is heatedby using a heater. Here, a heating temperature of the substrate W, forexample, can be in a range of 50° C. to 500° C. At this time, thetreatment gas including at least one of the reactant gas and the carriergas is supplied into the chamber 10. Here, examples of the carrier gasincluded in the treatment gas include at least one selected from thegroup consisting of helium (He) gas, argon (Ar) gas, and hydrogen (H₂)gas. In addition, the treatment gas further includes the reactant gas,in accordance with the type of surface modification that is performedwith respect to the thin film, and more specifically, may furtherinclude as the reactant gas at least one selected from the groupconsisting of oxygen (O₂) gas, nitrous oxide (N₂O) gas, carbon dioxide(CO₂) gas, nitrogen (N₂) gas, and ammonia (NH₃) gas. At this time, theenvironment in the chamber 10, for example, can be in a range of greaterthan or equal to 50 Pa, and can be preferably in a range of greater thanor equal to 300 Pa. And an upper limit thereof can be in a range of lessthan or equal to 1300 Pa, and can be preferably in a range of less thanor equal to 1000 Pa.

[Plasma Contact Step]

Next, the surface modification of the thin film is performed as theplasma contact step (the surface modification step) in which thetreatment gas is supplied into the chamber 10, and the high-frequencypower (the RF forward power (Fwd)) is applied to the gas supply unit 14,and thus, the reactant component in the treatment gas is subjected tothe plasma generation, and the treatment gas that is activated by theplasma generation is brought into contact with the thin film that isformed on the substrate W.

Here, When the reactant component of the treatment gas is subjected tothe plasma generation by applying the high-frequency power into thechamber, the third plasma generation condition is changed to the fourthplasma generation condition by performing at least one of graduallydecreasing the concentration of the reactant component and graduallyincreasing the power level of the high-frequency power. Accordingly, itis possible to perform the modification treatment with respect to thesurface of the thin film by using stable plasma of a higherconcentration, and thus, it is possible to efficiently perform a desiredmodification treatment with respect to the surface of the thin film.

A treatment in which gas including the carrier gas is used as thetreatment gas, and the treatment gas including the activated carrier gasis brought into contact with the surface of the thin film can beperformed as the modification treatment of the thin film surface. Suchtreatment gas is brought into contact with the thin film, and thus, thethin film is densified, and impurities are removed, and therefore, it ispossible to increase film quality of the thin film surface.

In addition, a treatment in which gas that includes reactant gasincluding constituent elements of the thin film and the carrier gas isused as the treatment gas, and the treatment gas including the activatedreactant gas is brought into contact with the thin film surface can beperformed as the modification treatment of the thin film surface. Suchtreatment gas is brought into contact with the thin film, and thus,atoms present at the thin film surface that have not been sufficientlyreacted can be further reacted, and therefore, it is possible toincrease the film quality of the thin film surface. For example, in acase where the thin film is a SiO₂ film, oxygen (O₂) gas that isactivated by the plasma generation is brought into contact with the thinfilm, and thus, silicon (Si) atoms that have not been sufficientlyoxidized can be further oxidized, and therefore, it is possible toincrease the film quality of the thin film surface.

In addition, a treatment in which gas that includes reactant gas notincluding the constituent elements of the thin film and the carrier gasis used as the treatment gas, and the treatment gas including theactivated reactant gas is brought into contact with the thin filmsurface can also be performed as the modification treatment of the thinfilm surface. Such treatment gas is brought into contact with the thinfilm, and thus, it is possible to change the constituent elements of thethin film surface. For example, in a case where the thin film is a SiO₂film, nitrogen (N₂) gas that is activated by the plasma generation isbrought into contact with the thin film, and thus, it is possible toform a nitride layer on the thin film surface.

The same condition as the condition of the plasma contact step in thefirst embodiment, the second embodiment, and the third embodiment can beused as the condition of the plasma contact step in this embodiment.

More specifically, as with the first embodiment of the method of forminga thin film, when the reactant component of the treatment gas issubjected to the plasma generation by applying the high-frequency powerinto the chamber, in the plasma contact step, the third plasmageneration condition in which high-frequency power of a fourth powerlevel that is identical to that of the fourth plasma generationcondition described below is applied while the treatment gas in whichthe concentration of the reactant component is a third concentration issupplied can be changed to the fourth plasma generation condition bygradually decreasing the concentration of the reactant component to afourth concentration from the third concentration while applying thehigh-frequency power of the fourth power level. Here, each of theconditions of the third concentration, the fourth concentration, and thefourth power level, configuring the third plasma generation conditionand the fourth plasma generation condition, can be set to the samecondition as that of the first concentration, the second concentration,and the second power level in the first embodiment of the method offorming a thin film.

In addition, as with the second embodiment of the method of forming athin film, when the reactant component in the treatment gas is subjectedto the plasma generation by applying the high-frequency power into thechamber, in the plasma contact step, the third plasma generationcondition in which the high-frequency power of the third power level isapplied or the high-frequency power is not applied while the treatmentgas in which the concentration of the reactant component is the fourthconcentration that is identical to that of the fourth plasma generationcondition described below is supplied can be changed to the fourthplasma generation condition by gradually increasing the power level ofthe high-frequency power to the fourth power level while the treatmentgas of the fourth concentration is supplied. Here, each of theconditions of the third power level, the fourth power level, and thefourth concentration, configuring the third plasma generation conditionand the fourth plasma generation condition, can be the same condition asthat of the first power level, second power level, and the secondconcentration in the second embodiment of the method of forming a thinfilm.

In addition, as with the third embodiment of the method of forming athin film, when the reactant component in the treatment gas is subjectedto the plasma generation by applying the high-frequency power into thechamber, in the plasma contact step, the first plasma generationcondition in which the high-frequency power of the first power level isapplied or the high-frequency power is not applied while the treatmentgas in which the concentration of the reactant component is the firstconcentration is supplied can be changed to the second plasma generationcondition by gradually increasing the power level of the high-frequencypower to the second power level from the first power level, and bygradually decreasing the concentration of the reactant component to thesecond concentration from the first concentration. Here, each of theconditions of the third concentration, the third power level, the fourthpower level, and the fourth concentration, configuring the third plasmageneration condition and the fourth plasma generation condition, can beset to the same condition as that of the first concentration, the firstpower level, the second power level, and the second concentration in thethird embodiment of the method of forming a thin film.

<<Combination of Method of Forming Thin Film and Method of ModifyingSurface of Thin Film>>

The surface modification step of the thin film described above may becombined with the deposition step of the thin film according to thefirst embodiment, the second embodiment, or the third embodiment.

More specifically, the method of forming a thin film may include a firstplasma contact step that is the deposition step of the thin film, and asecond plasma contact step that is the surface modification step of thethin film, as the plasma contact step. Among them, in the first plasmacontact step, the treatment gas including the reactant gas is suppliedinto the chamber, the reactant component in the treatment gas issubjected to the plasma generation by applying the high-frequency power,and the activated reactant component is brought into contact with theraw material gas component that is adsorbed on the substrate W to reactwith the raw material gas component, and thus, a thin film is formed. Inaddition, in the second plasma contact step, the treatment gas includingat least one of the reactant gas and the carrier gas is supplied intothe chamber, the reactant component in the treatment gas is subjected tothe plasma generation by applying the high-frequency power, and thetreatment gas including the activated reactant component is brought intocontact with the thin film that is formed on the substrate W, and thus,the thin film is subjected to a treatment.

Here, the first plasma contact step can be performed as with the plasmacontact step in the first embodiment, the second embodiment, or thethird embodiment of the method of forming a thin film described above.In addition, the second plasma contact step can be performed as with theplasma contact step in the embodiment of the surface modificationtreatment method of a thin film described above.

Note that, in the first plasma contact step, a thin film may be formedby using the treatment gas including the reactant gas and the carriergas, in accordance with the deposition step of the thin film accordingto the first embodiment, the second embodiment, or the third embodimentdescribed above, and then, the supply of the raw material gas, and asnecessary, the supply of the reactant gas may be stopped, and the thinfilm surface may be modified by using the carrier gas as the treatmentgas, in accordance with the surface modification step of the thin filmdescribed above. Accordingly, the surface modification step of the thinfilm can be performed by using the same film forming device, and byusing the same plasma generation condition as that of the firstembodiment, the second embodiment, or the third embodiment, and thus, itis possible to more efficiently deposit and modify the thin film.

EXAMPLES

Next, examples of the present invention will be described, however, thepresent invention is not limited to the examples and may includevariations providing such variations do not depart from the gist of theinvention.

Examples 1 to 6 of Present Invention

Examples 1 to 6 of the present invention are an example of the firstembodiment of the method of forming a thin film. FIG. 3 is a graphshowing the power level of the high-frequency power (the RF forwardpower (Fwd)) to be applied, and the concentration of oxygen (O₂) that isthe reactant component, in Examples 1 to 6 of the present invention. Thegraph is a graph at the time of changing a duration for maintaining thepower level after the concentration of the reactant component reachesthe second concentration (an RAMP time (1 second, 5 seconds, and 9seconds)) and the first concentration (20 volume % and 5 volume %) ofthe reactant component. Hereinafter, the details of test conditions andresults of Examples 1 to 6 of the present invention will be described.

Example 1 of Present Invention

As illustrated in FIG. 1 , the film forming device 1 was used in whichthe installation stand 12 of a diameter of 321 mm functioning as thelower electrode, on which the substrate W was installed on the uppersurface, and the gas supply unit 14 of a diameter of 347 mm functioningas the upper electrode were provided in the chamber 10. Here, the sizeof the air gap D between the installation stand 12 functioning as thelower electrode and the gas supply unit 14 functioning as the upperelectrode was 9.0 mm.

A silicon substrate of a diameter 300 mm was installed on theinstallation stand 12 in the chamber 10, as the substrate W, thesubstrate W was heated to a temperature of 300° C. by using the heaterembedded in the installation stand 12, and helium (He) gas was suppliedinto the chamber 10, as the carrier gas, and thus, the internal pressurewas reduced to 333 Pa.

A step of supplying raw material gas consisting of bis(diethylamino)silane (BDEAS) into the chamber 10 in which the pressure wasreduced, at a flow rate of 2000 sccm for a supply time of 0.2 seconds,was performed as the raw material gas supply step, and thus, a molecularlayer of the raw material gas was formed on the surface of the substrateW. After that, the purge step was performed in which the supply of theraw material gas was stopped, and the carrier gas (helium (He) gas) wassupplied into the chamber 10, and thus, the excessive raw material gascomponent that was not adsorbed on the substrate W was discharged fromthe chamber 10.

Next, the treatment gas including the carrier gas described above, andthe reactant gas was supplied into the chamber 10, and then, thehigh-frequency power was applied to the gas supply unit 14, and thus,the reactant component in the treatment gas was subjected to the plasmageneration, and was supplied onto the surface of the substrate W onwhich the raw material gas component was adsorbed, as the plasma contactstep. Here, the generation of plasma was performed by supplying thetreatment gas in which the concentration of the reactant component(oxygen (O₂) gas that was the reactant gas) was 20 volume % (the firstconcentration) and the remnant was formed of the carrier gas describedabove into the chamber 10, at a flow rate of 4000 sccm, by starting theapplication of the high-frequency power (the RF forward power (Fwd)) ofwhich the power level was 200 W (the second power level), and bydecreasing the concentration of the reactant component to 2 volume %(the second concentration) at a rate of change of 18 volume %/second.The high-frequency power was applied for 10 seconds after theconcentration of the reactant component reached the secondconcentration, and thus, a molecular layer formed of silicon oxide(SiO₂) was formed on the surface of the substrate W. After that, theby-product discharge step was performed in which the application of thehigh-frequency power was stopped, and the carrier gas (helium (He) gas)was supplied into the chamber 10, and thus, the by-product wasdischarged. FIG. 4 is a graph showing a variation in the power level ofthe high-frequency power (the RF forward power (Fwd)), the oxygen (O₂)concentration, and the flow rate of the raw material gas, in each of thesteps.

A set of steps from the raw material gas supply step to the by-productdischarge step were repeated 100 times, and thus, a thin film formed ofsilicon oxide (SiO₂) was formed.

As a result thereof, the self-bias voltage (Vdc) had 0 or a negativevalue while the thin film was formed, and thus, the abnormal electricaldischarge did not occur. In addition, the WERR of the obtained thin filmwas 1.8, and thus, it was possible to obtain a thin film of high filmquality.

Example 2 of Present Invention

The generation of the plasma in the plasma contact step was performed bysupplying the treatment gas in which the concentration of the reactantcomponent (oxygen (O₂) gas that was the reactant gas) was 20 volume %(the first concentration) and the remnant was the carrier gas formed ofthe carrier gas described above into the chamber 10, at a flow rate of4000 sccm, by starting the application of the high-frequency power (theRF forward power (Fwd)) of which the power level was 200 W (the secondpower level), and by decreasing the concentration of the reactantcomponent to 2 volume % (the second concentration) at a rate of changeof 3.6 volume %/second. The high-frequency power was applied for 5seconds after the concentration of the reactant component reached thesecond concentration, and thus, a molecular layer of silicon oxide(SiO₂) was formed on the surface of the substrate W.

The set of steps from the raw material gas supply step to the by-productdischarge step were repeated 100 times in the same condition as that ofExample 1 of the present invention except for the plasma contact step,and thus, a thin film formed of silicon oxide (SiO₂) was formed.

As a result thereof, the self-bias voltage (Vdc) had 0 or a negativevalue while the thin film was formed, and thus, the abnormal electricaldischarge did not occur. In addition, the WERR of the obtained thin filmwas 1.8, and thus, it was possible to obtain a thin film of high filmquality.

Example 3 of Present Invention

The generation of the plasma in the plasma contact step was performed bysupplying the treatment gas in which the concentration of the reactantcomponent (oxygen (O₂) gas that was the reactant gas) was 20 volume %(the first concentration) and the remnant was formed of the carrier gasdescribed above into the chamber 10, at a flow rate of 4000 sccm, bystarting the application of the high-frequency power (the RF forwardpower (Fwd)) of which the power level was 200 W (the second powerlevel), and by decreasing the concentration of the reactant component to2 volume % (the second concentration) at a rate of change of 2 volume%/second. The high-frequency power was applied for 1 second after theconcentration of the reactant component reached the secondconcentration, and thus, a molecular layer formed of silicon oxide(SiO₂) was formed on the surface of the substrate W.

The set of steps from the raw material gas supply step to the by-productdischarge step were repeated 100 times in the same condition as that ofExample 1 of the present invention except for the plasma contact step,and thus, a thin film formed of silicon oxide (SiO₂) was formed.

As a result thereof, the self-bias voltage (Vdc) had 0 or a negativevalue while the thin film was formed, and thus, the abnormal electricaldischarge did not occur. In addition, the WERR of the obtained thin filmwas 1.9, and thus, it was possible to obtain a thin film of high filmquality.

Example 4 of Present Invention

The generation of the plasma in the plasma contact step was performed bysupplying the treatment gas in which the concentration of the reactantcomponent (oxygen (O₂) gas that was the reactant gas) was 5 volume %(the first concentration) and the remnant was formed of the carrier gasdescribed above into the chamber 10, at a flow rate of 4000 sccm, bystarting the application of the high-frequency power (the RF forwardpower (Fwd)) of which the power level was 200 W (the second powerlevel), and by decreasing the concentration of the reactant component to2 volume % (the second concentration) at a rate of change of 3 volume%/second. The high-frequency power was applied for 9 seconds after theconcentration of the reactant component reached the secondconcentration, and thus, a molecular layer formed of silicon oxide(SiO₂) was formed on the surface of the substrate W.

The set of steps from the raw material gas supply step to the by-productdischarge step were repeated 100 times in the same condition as that ofExample 1 of the present invention except for the plasma contact step,and thus, a thin film formed of silicon oxide (SiO₂) was formed.

As a result thereof, the self-bias voltage (Vdc) had 0 or a negativevalue while the thin film was formed, and thus, the abnormal electricaldischarge did not occur. In addition, the WERR of the obtained thin filmwas 1.6, and thus, it was possible to obtain a thin film of high filmquality.

Example 5 of Present Invention

The generation of the plasma in the plasma contact step was performed bysupplying the treatment gas in which the concentration of the reactantcomponent (oxygen (O₂) gas that was the reactant gas) was 5 volume %(the first concentration) and the remnant was formed of the carrier gasdescribed above into the chamber 10, at a flow rate of 4000 sccm, bystarting the application of the high-frequency power (the RF forwardpower (Fwd)) of which the power level was 200 W (the second powerlevel), and by decreasing the concentration of the reactant component to2 volume % (the second concentration) at a rate of change of 0.6 volume%/second. The high-frequency power was applied for 5 seconds after theconcentration of the reactant component reached the secondconcentration, and thus, a molecular layer formed of silicon oxide(SiO₂) was formed on the surface of the substrate W.

The set of steps from the raw material gas supply step to the by-productdischarge step were repeated 100 times in the same condition as that ofExample 1 of the present invention except for the plasma contact step,and thus, a thin film formed of silicon oxide (SiO₂) was formed.

As a result thereof, the self-bias voltage (Vdc) had 0 or a negativevalue while the thin film was formed, and thus, the abnormal electricaldischarge did not occur. In addition, the WERR of the obtained thin filmwas 1.7, and thus, it was possible to obtain a thin film of high filmquality.

Example 6 of Present Invention

The generation of the plasma in the plasma contact step was performed bysupplying the treatment gas in which the concentration of the reactantcomponent (oxygen (O₂) gas that was the reactant gas) was 5 volume %(the first concentration) and the remnant was formed of the carrier gasdescribed above into the chamber 10, at a flow rate of 4000 sccm, bystarting the application of the high-frequency power (the RF forwardpower (Fwd)) of which the power level was 200 W (the second powerlevel), and by decreasing the concentration of the reactant component to2 volume % (the second concentration) at a rate of change of 0.33 volume%/second. The high-frequency power was applied for 1 second after theconcentration of the reactant component reached the secondconcentration, and thus, a molecular layer formed of silicon oxide(SiO₂) was formed on the surface of the substrate W.

The set of steps from the raw material gas supply step to the by-productdischarge step were repeated 100 times in the same condition as that ofExample 1 of the present invention except for the plasma contact step,and thus, a thin film formed of silicon oxide (SiO₂) was formed.

As a result thereof, the self-bias voltage (Vdc) had 0 or a negativevalue while the thin film was formed, and thus, the abnormal electricaldischarge did not occur. In addition, the WERR of the obtained thin filmwas 1.9, and thus, it was possible to obtain a thin film of high filmquality.

Examples 7 to 12 of Present Invention

Examples 7 to 12 of the present invention are an example of the secondembodiment of the method of forming a thin film. FIG. 6 is a graphshowing the power level of the high-frequency power (the RF forwardpower (Fwd)) to be applied, and the concentration of oxygen (O₂) that isthe reactant component, in Examples 7 to 12 of the present invention.The graph is a graph at the time of changing a duration for maintainingthe power level after the power level reached the second power level(the RAMP time (1 second, 5 seconds, and 9 seconds)) and the first powerlevel (0 W and 150 W). Hereinafter, the details of test conditions andresults of Examples 7 to 12 of the present invention will be described.

Example 7 of Present Invention

The generation of the plasma in the plasma contact step was performed bysupplying the treatment gas in which the concentration of the reactantcomponent (oxygen (O₂) gas that was the reactant gas) was 2 volume %(the second concentration) and the remnant was formed of the carrier gasdescribed above into the chamber 10, at a flow rate of 4000 sccm, bystarting the application of the high-frequency power (the RF forwardpower (Fwd)) of which the power level was 150 W (the first power level),and by increasing the power level to 200 W (the second power level) at arate of change of 50 W/second. The high-frequency power was applied for9 seconds after the power level of the high-frequency power reached thesecond power level, and thus, a molecular layer formed of silicon oxide(SiO₂) was formed on the surface of the substrate W.

The set of steps from the raw material gas supply step to the by-productdischarge step were repeated 100 times in the same condition as that ofExample 1 of the present invention except for the plasma contact step,and thus, a thin film formed of silicon oxide (SiO₂) was formed. FIG. 7is a graph showing a variation in the power level of the high-frequencypower (the RF forward power (Fwd)), the oxygen (O₂) concentration, andthe flow rate of the raw material gas, in each of the steps of Example 7of the present invention.

As a result thereof, the self-bias voltage (Vdc) had 0 or a negativevalue while the thin film was formed, and thus, the abnormal electricaldischarge did not occur. In addition, the WERR of the obtained thin filmwas 1.6, and thus, it was possible to obtain a thin film of high filmquality.

Example 8 of Present Invention

The generation of the plasma in the plasma contact step was performed bysupplying the treatment gas in which the concentration of the reactantcomponent (oxygen (O₂) gas that was the reactant gas) was 2 volume %(the second concentration) and the remnant was formed of the carrier gasdescribed above into the chamber 10, at a flow rate of 4000 sccm, bystarting the application of the high-frequency power (the RF forwardpower (Fwd)) of which the power level was 150 W (the first power level),and by increasing the power level to 200 W (the second power level) at arate of change of 10 W/second. The high-frequency power was applied for5 seconds after the power level of the high-frequency power reached thesecond power level, and thus, a molecular layer formed of silicon oxide(SiO₂) was formed on the surface of the substrate W.

The set of steps from the raw material gas supply step to the by-productdischarge step were repeated 100 times in the same condition as that ofExample 1 of the present invention except for the plasma contact step,and thus, a thin film formed of silicon oxide (SiO₂) was formed.

As a result thereof, the self-bias voltage (Vdc) had 0 or a negativevalue while the thin film was formed, and thus, the abnormal electricaldischarge did not occur. In addition, the WERR of the obtained thin filmwas 1.7, and thus, it was possible to obtain a thin film of high filmquality.

Example 9 of Present Invention

The generation of the plasma in the plasma contact step was performed bysupplying the treatment gas in which the concentration of the reactantcomponent (oxygen (O₂) gas that was the reactant gas) was 2 volume %(the second concentration) and the remnant was formed of the carrier gasdescribed above into the chamber 10, at a flow rate of 4000 sccm, bystarting the application of the high-frequency power (the RF forwardpower (Fwd)) of which the power level was 150 W (the first power level),and by increasing the power level to 200 W (the second power level) at arate of change of 5.5 W/second. The high-frequency power was applied for1 second after the power level of the high-frequency power reached thesecond power level, and thus, a molecular layer formed of silicon oxide(SiO₂) was formed on the surface of the substrate W.

The set of steps from the raw material gas supply step to the by-productdischarge step were repeated 100 times in the same condition as that ofExample 1 of the present invention except for the plasma contact step,and thus, a thin film formed of silicon oxide (SiO₂) was formed.

As a result thereof, the self-bias voltage (Vdc) had 0 or a negativevalue while the thin film was formed, and thus, the abnormal electricaldischarge did not occur. In addition, the WERR of the obtained thin filmwas 1.8, and thus, it was possible to obtain a thin film of high filmquality.

Example 10 of Present Invention

The generation of the plasma in the plasma contact step was performed bysupplying the treatment gas in which the concentration of the reactantcomponent (oxygen (O₂) gas that was the reactant gas) was 2 volume %(the second concentration) and the remnant was formed of the carrier gasdescribed above into the chamber 10, at a flow rate of 4000 sccm, and byincreasing the power level to 200 W (the second power level) from astate in which the high-frequency power (the RF forward power (Fwd)) wasnot applied (a state in which the first power level was 0 W), at a rateof change of 200 W/second. The high-frequency power of the second powerlevel was applied for 9 seconds after the power level of thehigh-frequency power reached the second power level, and thus, amolecular layer formed of silicon oxide (SiO₂) was formed on the surfaceof the substrate W.

The set of steps from the raw material gas supply step to the by-productdischarge step were repeated 100 times in the same condition as that ofExample 1 of the present invention except for the plasma contact step,and thus, a thin film formed of silicon oxide (SiO₂) was formed.

As a result thereof, the self-bias voltage (Vdc) had 0 or a negativevalue while the thin film was formed, and thus, the abnormal electricaldischarge did not occur. In addition, the WERR of the obtained thin filmwas 1.7, and thus, it was possible to obtain a thin film of high filmquality.

Example 11 of Present Invention

The generation of the plasma in the plasma contact step was performed bysupplying the treatment gas in which the concentration of the reactantcomponent (oxygen (O₂) gas that was the reactant gas) was 2 volume %(the second concentration) and the remnant was formed of the carrier gasdescribed above into the chamber 10, at a flow rate of 4000 sccm, and byincreasing the power level to 200 W (the second power level) from astate in which the high-frequency power (the RF forward power (Fwd)) wasnot applied (a state in which the first power level was 0 W), at a rateof change of 40 W/second. The high-frequency power of the second powerlevel was applied for 5 seconds after the power level of thehigh-frequency power reached the second power level, and thus, amolecular layer formed of silicon oxide (SiO₂) was formed on the surfaceof the substrate W.

The set of steps from the raw material gas supply step to the by-productdischarge step were repeated four times in the same condition as that ofExample 1 of the present invention except for the plasma contact step,and thus, a thin film formed of silicon oxide (SiO₂) was formed.

As a result thereof, the self-bias voltage (Vdc) had 0 or a negativevalue while the thin film was formed, and thus, the abnormal electricaldischarge did not occur. In addition, the WERR of the obtained thin filmwas 1.8, and thus, it was possible to obtain a thin film of high filmquality.

Example 12 of Present Invention

The generation of the plasma in the plasma contact step was performed bysupplying the treatment gas in which the concentration of the reactantcomponent (oxygen (O₂) gas that was the reactant gas) was 2 volume %(the second concentration) and the remnant was formed of the carrier gasdescribed above into the chamber 10, at a flow rate of 4000 sccm, and byincreasing the power level to 200 W (the second power level) from astate in which the high-frequency power (the RF forward power (Fwd)) wasnot applied (a state in which the first power level was 0 W), at a rateof change of 22 W/second. The high-frequency power of the second powerlevel was applied for 1 second after the power level of thehigh-frequency power reached the second power level, and thus, amolecular layer formed of silicon oxide (SiO₂) was formed on the surfaceof the substrate W.

The set of steps from the raw material gas supply step to the by-productdischarge step were repeated 100 times in the same condition as that ofExample 1 of the present invention except for the plasma contact step,and thus, a thin film formed of silicon oxide (SiO₂) was formed.

As a result thereof, the self-bias voltage (Vdc) had 0 or a negativevalue while the thin film was formed, and thus, the abnormal electricaldischarge did not occur. In addition, the WERR of the obtained thin filmwas 1.9, and thus, it was possible to obtain a thin film of high filmquality.

Examples 13 to 16 of Present Invention

Examples 13 to 16 of the present invention are an example of the methodof forming a thin film according to the third embodiment. FIG. 8 is agraph showing the power level of the high-frequency power (the RFforward power (Fwd)) to be applied and the concentration of oxygen (O₂)that is the reactant component, in Examples 13 to 16 of the presentinvention. The graph is a graph at the time of changing the firstconcentration (5% and 10%) of the reactant component, and the firstpower level (50 W and 150 W). Hereinafter, the details of testconditions and results of Examples 13 to 16 of the present inventionwill be described.

Example 13 of Present Invention

The generation of the plasma in the plasma contact step was performed bysupplying the treatment gas in which the concentration of the reactantcomponent (oxygen (O₂) gas that was the reactant gas) was 5 volume %(the first concentration) and the remnant was formed of the carrier gasdescribed above into the chamber 10, at a flow rate of 4000 sccm, bystarting the application of the high-frequency power (the RF forwardpower (Fwd)) of which the power level was 50 W (the first power level),and by decreasing the concentration of the reactant component to 2volume % (the second concentration) at a rate of change of 0.6 volume%/second and by increasing the power level to 200 W (the second powerlevel) at a rate of change of 30 W/second. The high-frequency power wasapplied for 5 seconds after the concentration of the reactant componentreached the second concentration and the power level of thehigh-frequency power reached the second power level, and thus, amolecular layer formed of silicon oxide (SiO₂) was formed on the surfaceof the substrate W.

The set of steps from the raw material gas supply step to the by-productdischarge step were repeated 100 times in the same condition as that ofExample 1 of the present invention except for the plasma contact step,and thus, a thin film of silicon oxide (SiO₂) was formed.

As a result thereof, the self-bias voltage (Vdc) had 0 or a negativevalue while the thin film was formed, and thus, the abnormal electricaldischarge did not occur. In addition, the WERR of the obtained thin filmwas 1.8, and thus, it was possible to obtain a thin film of high filmquality.

Example 14 of Present Invention

The generation of the plasma in the plasma contact step was performed bysupplying the treatment gas in which the concentration of the reactantcomponent (oxygen (O₂) gas that was the reactant gas) was 10 volume %(the first concentration) and the remnant was formed of the carrier gasdescribed above into the chamber 10, at a flow rate of 4000 sccm, bystarting the application of the high-frequency power (the RF forwardpower (Fwd)) of which the power level was 50 W (the first power level),and by decreasing the concentration of the reactant component to 2volume % (the second concentration) at a rate of change of 1.6 volume%/second and by increasing the power level to 200 W (the second powerlevel) at a rate of change of 30 W/second. The high-frequency power wasapplied for 5 seconds after the concentration of the reactant componentreached the second concentration and the power level of thehigh-frequency power reached the second power level, and thus, amolecular layer formed of silicon oxide (SiO₂) was formed on the surfaceof the substrate W.

The set of steps from the raw material gas supply step to the by-productdischarge step were repeated 100 times in the same condition as that ofExample 1 of the present invention except for the plasma contact step,and thus, a thin film formed of silicon oxide (SiO₂) was formed.

As a result thereof, the self-bias voltage (Vdc) had 0 or a negativevalue while the thin film was formed, and thus, the abnormal electricaldischarge did not occur. In addition, the WERR of the obtained thin filmwas 1.9, and thus, it was possible to obtain a thin film of high filmquality.

Example 15 of Present Invention

The generation of the plasma in the plasma contact step was performed bysupplying the treatment gas in which the concentration of the reactantcomponent (oxygen (O₂) gas that was the reactant gas) was 5 volume %(the first concentration) and the remnant was formed of the carrier gasdescribed above into the chamber 10, at a flow rate of 4000 sccm, bystarting the application of the high-frequency power (the RF forwardpower (Fwd)) of which the power level was 150 W (the first power level),and by decreasing the concentration of the reactant component to 2volume % (the second concentration) at a rate of change of 0.6 volume%/second and by increasing the power level to 200 W (the second powerlevel) at a rate of change of 10 W/second. The high-frequency power wasapplied for 5 seconds after the concentration of the reactant componentreached the second concentration and the power level of thehigh-frequency power reached the second power level, and thus, amolecular layer formed of silicon oxide (SiO₂) was formed on the surfaceof the substrate W.

The set of steps from the raw material gas supply step to the by-productdischarge step were repeated 100 times in the same condition as that ofExample 1 of the present invention except for the plasma contact step,and thus, a thin film formed of silicon oxide (SiO₂) was formed.

As a result thereof, the self-bias voltage (Vdc) had 0 or a negativevalue while the thin film was formed, and thus, the abnormal electricaldischarge did not occur. In addition, the WERR of the obtained thin filmwas 1.6, and thus, it was possible to obtain a thin film of high filmquality.

Example 16 of Present Invention

The generation of the plasma in the plasma contact step was performed bysupplying the treatment gas in which the concentration of the reactantcomponent (oxygen (O₂) gas that was the reactant gas) was 10 volume %(the first concentration) and the remnant was formed of the carrier gasdescribed above into the chamber 10, at a flow rate of 4000 sccm, bystarting the application of the high-frequency power (the RF forwardpower (Fwd)) of which the power level was 150 W (the first power level),and by decreasing the concentration of the reactant component to 2volume % (the second concentration) at a rate of change of 1.6 volume%/second and by increasing the power level to 200 W (the second powerlevel) at a rate of change of 10 W/second. The high-frequency power wasapplied for 5 seconds after the concentration of the reactant componentreached the second concentration and the power level of thehigh-frequency power reached the second power level, and thus, amolecular layer formed of silicon oxide (SiO₂) was formed on the surfaceof the substrate W.

The set of steps from the raw material gas supply step to the by-productdischarge step were repeated 100 times in the same condition as that ofExample 1 of the present invention except for the plasma contact step,and thus, a thin film formed of silicon oxide (SiO₂) was formed.

As a result thereof, the self-bias voltage (Vdc) had 0 or a negativevalue while the thin film was formed, and thus, the abnormal electricaldischarge did not occur. In addition, the WERR of the obtained thin filmwas 1.7, and thus, it was possible to obtain a thin film of high filmquality.

Comparative Example 1

The generation of the plasma in the plasma contact step was performed bysupplying the treatment gas in which the concentration of the reactantcomponent (oxygen (O₂) gas that was the reactant gas) was 2 volume % andthe remnant was formed of the carrier gas described above into thechamber 10, at a flow rate of 4000 sccm, and by starting the applicationof the high-frequency power (the RF forward power (Fwd)) of which thepower level was 200 W, without varying the concentration of the reactantcomponent and the power level of the high-frequency power. Thehigh-frequency power was applied for 10 seconds after the application ofthe high-frequency power was started, and thus, a molecular layer formedof silicon oxide (SiO₂) was formed on the surface of the substrate W.

The set of steps from the raw material gas supply step to the by-productdischarge step were repeated 100 times in the same condition as that ofExample 1 of the present invention except for the plasma contact step,and thus, a thin film formed of silicon oxide (SiO₂) was formed. FIG. 9is a graph showing a variation in the power level of the high-frequencypower (the RF forward power (Fwd)), the oxygen (O₂) concentration, andthe flow rate of the raw material gas, in each of the steps.

As a result thereof, as shown in FIG. 12 , the self-bias voltage (Vdc)had a positive value around 5 V while the high-frequency power wasapplied, and thus, the abnormal electrical discharge occurred. Inaddition, the WERR of the obtained thin film was 2.0, and thus, the filmquality was low.

Examples 17 and 18 of Present Invention

Examples 17 and 18 of the present invention are an example of a methodof forming a thin film according to a fourth embodiment. Hereinafter,the details of test conditions and results of Examples 17 and 18 of thepresent invention will be described.

Example 17 of Present Invention

A thin film formed of silicon oxide (SiO₂) was deposited on the siliconsubstrate by using the same film forming device 1 as that of Example 1of the present invention, in accordance with the same method as that ofComparative Example 1, and then, the supply of oxygen (O₂) gas that wasthe reactant gas was stopped, and only the supply of helium (He) gasthat was the carrier gas was performed, and thus, the internal pressurewas reduced to 333 Pa.

The carrier gas was subjected to the plasma generation by applying thehigh-frequency power to the gas supply unit 14 while the treatment gasformed of the carrier gas that was the reactant component was suppliedinto the chamber 10 in which the pressure was reduced, and was suppliedonto the surface of the substrate W on which the raw material gascomponent was adsorbed, as the plasma contact step. Here, the generationof plasma was performed by supplying the carrier gas into the chamber 10at a flow rate of 4000 sccm, by starting the application of thehigh-frequency power (the RF forward power (Fwd)) of which the powerlevel was 150 W (the first power level), and by increasing the powerlevel to 200 W (the second power level) at a rate of change of 50W/second. The high-frequency power was applied for 9 seconds after thepower level of the high-frequency power reached the second power level,and thus, the thin film formed of silicon oxide (SiO₂) that wasdeposited on the surface of the substrate W was densified, and theimpurities were removed, and therefore, a treatment of increasing thefilm quality was performed. FIG. 10 is a graph showing a variation inthe power level of the high-frequency power (the RF forward power(Fwd)), the oxygen (O₂) concentration, and the flow rate of the rawmaterial gas, in each of the steps.

As a result thereof, the self-bias voltage (Vdc) had 0 or a negativevalue while the thin film was formed, and thus, the abnormal electricaldischarge did not occur. In addition, the WERR of the thin film afterthe treatment was 1.7, and thus, it was possible to obtain a thin filmof desired high film quality.

Example 18 of Present Invention

A thin film formed of silicon oxide (SiO₂) was deposited on the siliconsubstrate by using the same film forming device 1 as that of Example 1of the present invention, in accordance with the same method as that ofComparative Example 1, and then, the plasma contact step was performedby supplying the treatment gas in which the concentration of thereactant component (oxygen (O₂) gas that was the reactant gas) was 2volume % and the remnant was formed of the carrier gas described aboveinto the chamber 10 in which the pressure was reduced, at a flow rate of4000 sccm, by starting the application of the high-frequency power (theRF forward power (Fwd)) of which the power level was 20 W (the secondpower level), and by decreasing the concentration of the reactant gas to2 volume % (the second concentration) at a rate of change of 9 volume%/second. The high-frequency power was applied for 18 seconds after theconcentration of the reactant gas reached the second concentration, andthus, silicon (Si) atoms that had not been sufficiently oxidized,included in the surface of the thin film formed of silicon oxide (SiO₂)that was deposited on the surface of the substrate W, was furtheroxidized, and thus, the treatment of increasing the film quality wasperformed. FIG. 11 is a graph showing a variation in the power level ofthe high-frequency power (the RF forward power (Fwd)), the oxygen (O₂)concentration, and the flow rate of the raw material gas, in each of thesteps.

As a result thereof, the self-bias voltage (Vdc) had 0 or a negativevalue while the thin film was formed, and thus, the abnormal electricaldischarge did not occur. In addition, the WERR of the thin film afterthe treatment was 1.9, and thus, it was possible to increase the filmquality of the thin film.

Conclusion

From the results described above, it was confirmed that in the method offorming a thin film (Examples 1 to 18 of Present Invention) in which theabnormal electrical discharge is suppressed by increasing thehigh-frequency power to the second power level, by gradually decreasingthe treatment gas to the second concentration, and/or, by graduallyincreasing the high-frequency power to the second power level, from thefirst plasma generation condition in which stable plasma was generated,it was possible to obtain a thin film of higher film quality, and toobtain a desired thin film, compared to the method of forming a thinfilm of Comparative Example 1.

EXPLANATION OF REFERENCE NUMERALS

-   -   1 FILM FORMING DEVICE    -   10 CHAMBER    -   11 INSERTION HOLE    -   12 INSTALLATION STAND    -   13, 16 SUPPORT MEMBER    -   14 GAS SUPPLY UNIT    -   15 GAS SUPPLY HOLE    -   W SUBSTRATE    -   D AIR GAP

What is claimed is:
 1. A method of forming a thin film on a surface of asubstrate, the method comprising: a plasma contact step includingsupplying a treatment gas including a reactant gas into a chamber,activating a reactant component included in the treatment gas bygenerating plasma from the reactant component by applying high-frequencypower, and bringing the treatment gas including the reactant componentthus activated into contact with the surface of the substrate to formthe thin film, wherein in the plasma contact step, a first plasmageneration condition is changed to a second plasma generation conditionby adjusting at least one of concentration of the reactant componentincluded in the treatment gas and power level of the high-frequencypower, thereby suppressing abnormal electrical discharge.
 2. The methodof claim 1, wherein in the first plasma generation condition,high-frequency power of a second power level that is identical to thatof the second plasma generation condition is applied while treatment gasin which the concentration of the reactant component is a firstconcentration is supplied, and the concentration of the reactantcomponent is decreased to a second concentration from the firstconcentration while the high-frequency power of the second power levelis applied, to thereby change the first plasma generation condition tothe second plasma generation condition.
 3. The method of claim 1,wherein in the first plasma generation condition, high-frequency powerof a first power level is applied or the high-frequency power is notapplied while treatment gas in which the concentration of the reactantcomponent is a second concentration that is identical to that of thesecond plasma generation condition is supplied, and the power level ofthe high-frequency power is increased to a second power level while thetreatment gas of the second concentration is supplied, to thereby changethe first plasma generation condition to the second plasma generationcondition.
 4. The method of claim 1, wherein in the first plasmageneration condition, high-frequency power of a first power level isapplied or the high-frequency power is not applied while treatment gasin which the concentration of the reactant component is a firstconcentration is supplied, and the power level of the high-frequencypower is increased to a second power level from the first power level,and the concentration of the reactant component is decreased to a secondconcentration, to thereby change the first plasma generation conditionto the second plasma generation condition.
 5. The method of claim 1,further comprising: before the plasma contact step, a supply step ofsupplying at least a raw material gas including a raw material gascomponent into the chamber and adsorbing the raw material gas componenton the surface of the substrate; and a discharge step of discharging anyof the raw material gas component that is not adsorbed on the surface ofthe substrate from the chamber, wherein the plasma contact step is athin film deposition step performed by a plasma-enhanced atomic layerdeposition (PEALD) process in which the treatment gas including thereactant gas supplied into the chamber also includes a carrier gas, thereactant component consists of at least one of the reactant gas and thecarrier gas, activation of the reactant component includes generatingplasma from the reactant component by applying high-frequency power, andthe reactant component thus activated reacts with the raw material gascomponent that is adsorbed on the surface of the substrate to form thethin film.
 6. The method of claim 5, wherein the raw material gas isaminosilane.
 7. The method of claim 5, wherein the reactant gas is atleast one selected from the group consisting of oxygen (O₂) gas, nitrousoxide (N₂O) gas, carbon dioxide (CO₂) gas, nitrogen (N₂) gas, andammonia (NH₃) gas.
 8. The method of claim 5, wherein the carrier gas isat least one selected from the group consisting of helium (He) gas,argon (Ar) gas, and hydrogen (H₂) gas.
 9. The method of claim 1, whereinthe thin film consists of a SiO₂ film, a SiN film, or a SiC film.
 10. Amethod of modifying a surface of a thin film formed on a substrate, themethod comprising: a plasma contact step including supplying treatmentgas including at least one of a reactant gas and carrier gas into achamber, activating the treatment gas by generating plasma by applyinghigh-frequency power to the treatment gas, and bringing the treatmentgas thus activated by the generation of plasma into contact with thesurface of the thin film formed on the substrate to modify the surfaceof the thin film, wherein the plasma contact step is a surfacemodification step in which a third plasma generation condition ischanged to a fourth plasma generation condition by adjusting at leastone of concentration of a reactant component included in the treatmentgas and power level of the high-frequency power, thereby suppressingabnormal electrical discharge.